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                [2012北大校赛]Do Not Gamble                </h1>
                <p>时间限制：10s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><div>Have you ever gambled? I wish you not. Being a professional gambler for three years, I learned every</div>
<div>&nbsp;trick they play. Gambling is has nothing to do with luck. It is all about cheating.One of the most&nbsp;</div>
<div>elementary tricks is &quot;mercury dice&quot;. Instead of being solid, there is a hollow chamber, filled with&nbsp;</div>
<div>mercury, inside of the dice. This little modification makes the dice asymmetric, so that, the probab</div>
<div>ility of each outcome is not equal. Imprecisely, which face is up, depends on the previous state.To&nbsp;</div>
<div>simplify the model, we use &quot;mercury coin&quot; here. As we mentioned, the state (head or tail) after toss</div>
<div>ing depends on the state before. The probability of that the two states are same, is p. For example,</div>
<div>&nbsp;if the head side is up now, the probability that, the coin is still head up after tossing is p. And</div>
<div>&nbsp;the probability that the tail side come up is 1-p. If p=0.5, it is a common coin. When p&ne; 0.5, thi</div>
<div>s coin is mercury coin. Assume the coin is head up now. After we toss Ntimes, what is the probabilit</div>
<div>y that, the number of heads is less than a certain number K?</div>
<p></p></p><hr/><h3>输入格式</h3><p><div>The test file contains multiple lines, and each line is a test case.&nbsp;</div>
<div>Each test cases consists of three numbers</div>
<div>N K p</div>
<div>N and K are integers, and p is a float number.&nbsp;</div>
<div>N &le; 30000</div>
<div>K &le; N</div>
<div>0 &le; p &le; 1</div></p><hr/><h3>输出格式</h3><p><p></p>
<p></p>
<p>
<dt>
<div>For each test case, output the probability that, after tossing N times, the number of heads is less&nbsp;</div>
<div>than K. Rounded to the three digit after the decimal point.</div>
</dt>
</p>
<p></p>
<p></p></p><hr/><h3>样例输入</h3><pre>171 88 0.107
</pre><hr/><h3>样例输出</h3><pre>0.83785</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>没有写明来源</p>
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